Nanosensor is an extremely small device capable of detecting and responding to physical stimuli with dimensions on the order of one billionth of a meter. Physical Stimuli: biological and chemical substances, displacement, motion, force, mass, acoustic, thermal, and electromagnetic. Major advantages of Nanosensors are, they are Smaller, Require less power to run, Greater sensitivity, Better specificity. Nanosensors are any biological, chemical, or surgical sensory points used to convey information about nanoparticles to the macroscopic world. Their use mainly include various medicinal purposes and as gateways to building other nanoproducts, such as computer chips that work at the nanoscale and nanorobots. There are several ways being proposed today to make nanosensors; these include top-down lithography, bottom-up assembly, and molecular self-assembly. An active nanosensor would have the ability to send a signal that could be received remotely. For example, an embedded nanosensor in a stationary position in a water reservoir, lake, or stream could detect the presence of a dangerous pathogen and send a signal. A passive nanosensor would rely on observation of a change in color, opacity, or fluorescence. Major Application: Transportation, Communications, Integrated Circuits, Building and Facilities, Medicine Safety, National Security, Aerospace.